The present invention relates to an automatic dishwasher for sequentially washing and rinsing dishes or other articles to be washed.
Currently commercially available automatic dishwashers are generally classified into two types, i.e., tank system and fresh water supply system, depending on the piping system used therein.
An example of the prior art dishwashers of tank system is disclosed in, for example, the Japanese Laid-open Patent Publication No. 57-139315, published Aug. 28, 1982, and is schematically shown in FIG. 1 of the accompanying drawings. As shown in FIG. 1, the prior art dishwasher with a tank system is so designed that, after a washing solution (containing a detergent) within a solution tank T has been pumped by a circulating pump P1 towards spray nozzle assemblies N1 and then sprayed onto articles supported in a rack R to wash the articles, the sprayed washing solution is recovered in the solution tank T for recirculation towards the nozzle assemblies N1 through the circulating pump P1, thereby bringing the washing action on the articles. After the washing operation, a fresh rinsing water supplied through a supply pipe L1 into a booster (heating device) B and heated therein is supplied under pressure towards spray nozzle assemblies N2 through a water supply pipe L2, which is separate from the supply pipe for the flow of the washing solution, and then sprayed onto the articles in the rack R to rinse the articles. The washing solution remaining in the tank T is allowed to overflow into an overflow tube OT for discharging a quantity of washing solution required to accomodate the sprayed rinsing water in the tank T.
In this prior art dishwasher shown in FIG. 1, as a source of pressure necessary to supply the rinsing water from the booster B towards the nozzle assemblies N2, either the pressure of water supplied from a water main to the dishwasher, or a pump such as shown by P2 which is separate from the circulating pump P1, is employed.
Thus, the prior art dishwasher shown in FIG. 1 requires the use of two separate pumps for the washing and rinsing operations, respectively, resulting in increased manufacturing cost. In a prior art dishwasher in which from a water main is employed for supplying the rinsing water while only one pump is used for the washing operation, the rinsing efficiency tends to be adversely affected by fluctuating water main pressure and, therefore, an extra pressure control device for regulating the water pressure to a predetermined value is required, thereby resulting not only in greater complexity of the dishwasher as a whole but also increased manufacturing cost.
Moreover, since the two separate pipe lines are used for the supply of the washing solution and the rinsing water, not only is the number of the component parts used increased with the consequence of the correspondingly increased manufacturing cost, but also time-consuming and complicated procedures are required to clean the dishwasher, particularly the piping system including the separate pipe lines and the nozzle assemblies.
On the other hand, an example of prior art dishwashers of fresh water supply system is disclosed in, for example, the U.S. Pat. No. 3,465,762, patented Sept. 9, 1969, and is schematically shown in FIG. 2 of the accompanying drawings. The prior art dishwasher shown in FIG. 2 is so designed that, after the washing solution within the solution tank T has been pumped by a pump P towards a spray nozzle assembly N and then sprayed onto the articles supported in the rack R to wash the articles, the sprayed washing solution is recovered in the tank T for recirculaton towards the nozzle assembly N, thereby applying a washing action to the articles. After the completion of the washing operation, an electromagnetic valve EV disposed on a drain pipe DP is opened to drain the total quantity of washing solution within the tank T, whereupon a hot water is introduced through a hot water supply line La into the tank T. When the amount of the hot water so introduced attains a predetermined level within the tank T, the pump P is again operated to apply a rinsing action to the articles.
Although the dishwasher with a fresh water supply system is advantageous in that only one pump can be utilized for both washing and rinsing operations, food solids removed from the articles having been washed into the tank T are apt to be mixed with the rinsing water, reducing the rinsing efficiency. In addition thereto, a relatively long time including the time required to drain the washing solution and the time required to supply the rinsing water tends to be consumed subsequent to the completion of the washing operation and before the start of the rinsing operation, and moreover, the total amount of the water within the tank has to be drained each time any one of the washing and rinsing operations has been completed. Accordingly, the prior art dishwasher of the type shown in FIG. 2 has an additional disadvantage in that a relatively large amount of water is consumed with increased running cost required.